Etiological agents responsible for various infections and other diseases, such as syphilis can be detected in a test referred to as a rapid plasma reagin (RPR) test. One specific such assay is known as a BD Macro-Vue RPR test provided by Becton Dickinson and Company of Franklin Lakes, N.J. The RPR test is a non-treponemal flocculation test that is used to detect and quantify reagin, an antibody present in serum or plasma as a screen test for syphilis. The etiological agent responsible for syphilis produces at least two kinds of antibodies in human infections. The treponemal antibodies can be detected by florescent treponemal antibody-absorption (FTA-ABS) test whereas the reagin antibody is detected by the RPR antigen test. In the presence of the reagin antibody and the reactive sample, the RPR antigen preparation will produce flocculation consisting of black clumps against the white background of a test card. By contrast, non-reactive samples will yield an even light gray homogenous suspension.
The RPR test known in the prior art is performed upon EDTA plasma and unheated or heated serum. The specimen should be free of bacterial contamination and haemolysis. A reagent is also utilized in the test. One such reagent is an RPR carbon antigen formed of 0.003 percent cardiolipin, 0.020-0.022 percent lecithin, 0.09 percent cholesterol, 0.0125 M EDTA, 0.1 MNa2HPO4, 0.01 MKH2PO4, 0.1 percent thimerosal, 0.0188 percent charcoal and ten percent choline chloride.
In performing the test the specimen and the reagent are combined together on a test card, such as by applying a drop of each onto the test card. The sample and antigen reagent are not mixed. Rather, they are put onto an automatic rotator, preferably under a humidity cover, with the rotator rotating the combination of the sample and reagent at 100 rpm for eight minutes. Following rotation, a brief hand rotation and tilting of card (three to four times) should be made to aid in differentiating non-reactive from minimally reactive results. Results are then read by studying the combination of the sample and the reagent. A non-reactive sample will have no clumping of the carbon particles in the reagent or very slight roughness, with a smooth gray overall appearance. If the sample is reactive, presence of large aggregates of carbon particles will be visually detected and usually against a clear background. A reactive specimen is considered to have undergone agglutination. In a more detailed variation of the test for more quantitative results, the sample is diluted two to one, four to one, eight to one, sixteen to one, etc. and the reagent is added and after rotation the sample is read for agglutination. In such a test those specimens which are non-reactive can be distinguished from those which are reactive and also minimally reactive specimens can be identified where there is a presence of small or fine aggregates of carbon particles.
Such a test involves combining a sample of a prepared blood product with an appropriate reagent that includes carbon (e.g. charcoal) particles therein. The reagent may or may not react with the specimen by undergoing flocculation. If the carbon particles become trapped in the flocculation and appear agglutinated or as black clumps against a light background, the specimen is considered to be reactive with the reagent. If the reagent maintains a uniform light gray color with even particle distribution and no clumping, it is indicative of a non-reactive specimen.
RPR tests, are currently known to be performed manually and to involve a variety of steps where the potential for human error or variation in manual performance of the test can result in less reliable results. Also, the test is significantly time intensive even when properly performed, requiring significant amounts of time expenditure by well trained practitioners. Accordingly, a need exists for an RPR test which produces a result which can be more easily read reliably by personnel with less training. Furthermore, a need exists to automate the RPR test to more rapidly and reliably conduct tests with fewer skilled operator hours being required. Furthermore, it is desirable to have test results archived in a variety of different ways for later analysis and for verification of test results. By automating the RPR test, an opportunity is presented for high quality archiving of large numbers of assays for efficient and reliable management of test results from RPR tests or agglutination assays.